The invention relates to a synchronizing shift clutch toothing arrangement for use with change-speed transmissions for automotive vehicles and the like.
In known clutch toothings of this type (U.S. Pat. No 3,737,016), there is often the problem that, in terms of time, after the synchronism of the clutch halves which is obtained by means of the synchronizing means, and therefore when the blocking effect of the blocking teeth is cancelled, one of the two clutch halves can assume a synchronously unstable state as a result of external forces and therefore be incited to renewed relative rotation in relation to the other clutch half, even before the clutch teeth have come into engagement. Because of this relative rotation cancelling the synchronism, during the further shifting cycle disturbing noises or even material damage to the tooth ends occur at that moment when the latter butt against one another. Thus, in motor vehicle transmissions with a clutch toothing of the relative generic type, the so-called "cold scraping" is known in a one-to-two shift at relatively low outside temperatures. This phenomenon is caused by the fact that, after completed synchronism, as a result of the braking effect of the cold highly viscous transmission oil, the rotational speed of the shift gear wheel to be coupled to its transmission shaft during this shift decreases in relation to the constant rotational speed of the transmission shaft, as result of which, during the further actuation of the shift sleeve, the sloping faces of the tooth ends scratch against one another and thus produce the so-called "cold scraping".
In a known clutch toothing of a different generic type (German Patent No. 3,444,670), this problem is to be eliminated by making the blocking faces on the clutch ring fixed in terms of movement relative to the shift sleeve and having the synchronizing ring asymmetric, so that the blocking faces, at the front in relation to the running direction, have a greater axial extent than the blocking faces at the rear in relation to the running direction. This design necessitates a relatively large constructional length and cannot reliably prevent the so-called "cold scraping".
An object on which the invention is based is essentially, in clutch toothings in the type mentioned in the introduction, to prevent the above-mentioned disadvantages as regards disturbing noises, etc. in the shift phase between synchronism and the start of engagement, without increasing the constructional length.
According to the invention, this object is advantageously achieved by an arrangement wherein the vertex on the synchronously unstable clutch ring is offset in the direction of the relative rotation cancelling the synchronism and the vertex on the other clutch ring is offset in the opposite direction in relation to the tooth mid-plane, containing the clutch axis, of the respective clutch tooth.
In the clutch toothing according to preferred embodiments of the invention, the axial force components on the sloping faces, which counteract insertion in the shift phase mentioned, are reduced substantially, so that the clutch toothing of the synchronously unstable clutch ring incitable to renewed relative rotation is virtually intercepted by the clutch toothing of the other ring.
This intercepting effect is the most effective when the clutch toothing according to the invention has a design wherein the vertex of the angle of the sloping face is in the plane of the tooth flank offset in the same direction relative to the tooth mid-plane. In this arrangement, an axial repulsion of the clutch ring executing the shifting movement, that is to say the engaging movement, can no longer occur.
According to another advantageous design of preferred embodiments of the clutch toothing according to the invention, an arrangement is provided wherein the tooth has two angled sloping end faces the smaller of the two sloping faces forms with the plane of its adjacent tooth flank an angle of approximately 22.degree.. This arrangement is preferred especially for those shift clutches, in which shifts occur with a differing direction of rotation of the synchronously unstable clutch halves, as happens, for example, in one-to-two upshifts and three-to-two down shifts of motor vehicle transmissions. In these cases, the shift gear wheel of the second gear has a higher rotational speed in the first gear and a lower rotational speed in the third gear than its transmission shaft, and therefore in downshifts there is no way of preventing the possibility that repulsion forces will be detectable on the larger sloping face, which in this shift operation has to perform the function of insertion, because of a possible too low inclination in relation to the peripheral direction. These disadvantages are avoided in the design of the clutch toothing according to the above noted preferred embodiments of the invention.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.